Cathodoluminescence from interlayer excitons in a 2D semiconductor heterobilayer

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Photoluminescence is a common technique for studying excitons in 2D materials like transition metal dichalcogenide (MX2) monolayers.
• Interlayer excitons can form in heterobilayers of different MX2 monolayers, exhibiting unique properties such as long lifetimes and field tunability.
• Moiré patterns in twisted heterobilayers can trap these interlayer excitons.

Purpose of the Study:

• To demonstrate the observation of interlayer exciton emission in a WSe2/MoSe2 heterobilayer using cathodoluminescence.
• To leverage the high spatial resolution of cathodoluminescence for analyzing sample heterogeneity and moiré patterns in 2D heterostructures.

Main Methods:

• Fabrication of a WSe2/MoSe2 heterobilayer encapsulated in hexagonal boron nitride.
• Utilizing cathodoluminescence (CL) spectroscopy and imaging to probe the optical emission from the heterobilayer.
• Comparing the spatial resolution of CL with photoluminescence for analyzing nanoscale features.

Main Results:

• Successful observation of radiative recombination emission from interlayer excitons in the WSe2/MoSe2 heterobilayer via cathodoluminescence.
• Demonstration that cathodoluminescence provides superior spatial resolution (100s of nm) compared to photoluminescence.
• Detailed analysis of sample heterogeneity and variations in twist angles across the heterostructure.

Conclusions:

• Cathodoluminescence is a powerful tool for spatially resolved studies of interlayer excitons in 2D heterobilayers.
• The technique enables detailed characterization of moiré potentials and their influence on exciton behavior.
• Understanding these nanoscale variations is crucial for designing and optimizing future 2D electronic and optoelectronic devices.